1. Field of the Invention
This invention relates to probe tips for circuit testing, and, more particularly to a probe tip providing dual contact paths within a flying probe tester.
2. Background Information
Probe configurations for establishing contact with electronic circuits during testing processes are typically formed either as ganged probes or flying probes. With ganged probes, a number, which may be a large number, of probe contacts simultaneously contact the circuit being tested at a corresponding number of different points. Individual tests are performed in a sequential manner by switching these individual probes to test circuits within the testing apparatus. With flying probes, a relatively small number of probes, typically two, are moved among the various circuit points to be connected to the test circuits in a sequential manner. Each of the flying probes contacts a single circuit test point at a time.
A particular form of testing which has found value in a number of applications is known as four-point or Kelvin testing. In this process, testing occurs between two points in a circuit under test, with each of these points being simultaneously contacted by two probe points from a single probe assembly. These two probe points are electrically isolated from one another, with a drive signal being applied to the circuit under test through one of the probe points. A sensing signal is provided to a test circuit within the test apparatus through the other of the probe points. This sensing signal may be provided to high impedance circuits within the test apparatus, so that little current is drawn, minimizing the effect of contact resistance on the measurements being made.
Regardless of the testing method used, electronic circuits are becoming smaller but more complex. For ganged probes, these changes mean that increasing numbers of probes must contact points within a smaller space. The probes must be smaller, closer together, and more accurately spaced, since the circuit pads on which they are placed must be smaller. For flying probes, these changes mean that, since more circuits must be tested, the probes must be moved from one position to another more rapidly to facilitate an efficient testing process. Thus, the flying probe itself must by quite light to allow rapid acceleration. Furthermore, what is needed is a method for making the electrical connections between a flying probe and the circuit points more reliable and repeatable.
What is needed is a miniature probe facilitating the application of the Kelvin testing process within a high-speed flying-probe circuit tester.